1. Field of the Invention
The present technology relates to high density memory devices based on phase change memory materials, like chalcogenides, and on other programmable resistance materials, and methods for manufacturing such devices.
2. Description of Related Art
In some programmable resistance memory array configurations, each memory cell includes a diode in series with a phase change memory element. The diode acts as a driving device, so that memory cells can be selected for operation by forward bias on the diode, while current flow in unselected memory cells is blocked by reverse bias on the diode. The phase change memory element is made of phase change materials that exhibit a large resistivity contrast between crystalline (low resistivity) and amorphous (high resistivity) states.
In normal operation of a phase change memory element, an electrical current pulse passed through the phase change memory cell and the diode driving device can set or reset the phase change memory element. To reset the memory element into the amorphous phase, an electrical current pulse with a large magnitude for a short time period can be used to heat up an active region of the memory element to a melting temperature, and then cause it to solidify in the amorphous phase. To set the memory element into the crystalline phase, an electrical current pulse with a medium magnitude, which causes it to heat up to a crystallization transition temperature, and a longer time period can be used allowing the active region to solidify in a crystalline phase. To read the state of the memory element, a small voltage is applied to the selected cell and the resulting electrical current is sensed.
Diodes have been used as semiconductor memory driving devices. Typically, manufacturing technology used to make diode driving devices includes line patterning or hole fill-in. Such technology can require advanced lithography tools or multiple patterning processes to make diodes on small scales and accordingly is not suitable for scalability.
It is desirable to provide diode driving device structures for scalability in high density memory devices.